The present subject matter relates generally to axles for vehicles and more particularly to fabricated axles for vehicles and processes for making same.
Typical steer axle assemblies for vehicles include a forged I-beam axle, and a pair of steering knuckles pivotally attached to opposite ends of the axle by way of king pins. Although they are generally strong and reliable, such forged I-beam axles are limited in their shape, are relatively heavy, and require a relatively large amount of machining. All of this translates into increased manufacturing and payload costs.
In view of the foregoing, fabricated axles have been developed. Such axles are typically manufactured from sheets of steel that are cut and then welded together. Fabricated axles generally weigh less than forged I-beam axles. For at least one known application, a forged I-beam steering axle for use with heavy-duty trucks weighs approximately one hundred ninety-five pounds, whereas an equivalent typical fabricated axle weighs approximately one hundred twenty-five pounds. In the case of commercial vehicles, including heavy-duty truck commercial vehicles, this translates into substantially increased payload capacity.
Another benefit of fabricated axles is that the material used (e.g., steel) can be spread around for more efficient distribution thereof. This can contribute to making the fabricated axle much lighter, and can even make it stiffer against both bending and torsion stresses. On top of all this, fabricated axles typically require less machining than forged I-beam axles. Accordingly, they are easier and less expensive to manufacture.
An example of a known fabricated axle is shown and described in U.S. Pat. No. 5,810,377, which is hereby incorporated herein by reference. The fabricated axle disclosed therein was a marked improvement over what was then the prior art and it is still useful for most purposes. However, it has now been recognized to have certain deficiencies. Principally, that fabricated axle does not utilize material optimally, causing increased costs in manufacture and material waste.
This disadvantage led to the development of further improved designs. For example, the fabricated axle shown and described in U.S. Pat. No. 6,609,764, which is hereby incorporated herein by reference, addressed many of said deficiencies. In particular, the axle described in U.S. Pat. No. 6,609,764 employs a main body formed from a rectangular blank, with only a small amount of the blank being wasted.
While the axle described in U.S. Pat. No. 6,609,764 successfully reduced the amount of waste material, it was not without its own disadvantages. For example, the main body of the axle is relatively short, thus requiring the attachment of a number of relatively heavy components, such as a pair of top king pin plates and gooseneck parts. Additionally, the multiplicity of components may increase manufacturing costs and complexity. For example, one manufacturing process is described as employing a three-pass weld to secure the various components to each other.
FIG. 1 illustrates a portion of yet another known fabricated vehicle axle A. The axle A includes a straight main body B having a U- or C-shaped cross-section and a continuous bottom plate P secured thereto. Separate goosenecks G (only one of which is illustrated) are welded to the ends of the main body B and to the bottom plate P. The goosenecks G are provided as cast components having a forked portion F, which provides an additional location by which to weld the gooseneck G to the main body B. In addition to their already heavy composition, the cast goosenecks G provide a relatively abrupt transition at the ends of the main body B, which further increases the weight of the axle A by requiring a three-pass weld to secure the gooseneck G and a portion of the main body B to the bottom plate P and rendering the material M under the gooseneck G redundant and effectively wasted.
FIG. 2 illustrates a portion of still another fabricated vehicle axle A′. This axle A′ is described in U.S. Pat. No. 7,862,058, the full disclosure of which is hereby incorporated herein by reference. The axle A′ includes a main body B′ having a U- or C-shaped cross-section and a continuous bottom plate P′ secured thereto. Main body B′ includes a relatively elongated gooseneck portion G′ and extends to the head of axle A′. A king pin fixture K having a substantially cylindrical shape is illustrated. King pin fixture K is secured to gooseneck portion G′, thereby minimizing the size of the king pin fixture. This axle A′ has the advantage of a simple cylindrical machined head that easily can be made solid for tapered king pin applications. Nonetheless, the axle A′ (and particularly the kingpin fixture of axle A′) may not be as robust as may be required for some applications.
It is desirable to overcome one or more of the foregoing shortcomings, or alternatively other shortcomings not specified herein but associated with prior fabricated axles.